The present disclosure relates to a developing device which supplies developer to an image carrier, and an electro-photographic image forming apparatus including the same.
An electro-photographic image forming apparatus forms an electrostatic latent image by irradiating a photosensitive layer formed on a surface of a photosensitive drum (image carrier) with light based on image information read from an original document, or image information obtained, by transmission and so on, from an external device such as a computer. The image forming apparatus supplies toner from the developing device to the electrostatic latent image to form a toner image, and then transfers the toner image onto a sheet (recording medium). The sheet that has gone through the transfer process is then subjected to toner-image fixing process, to be then discharged to outside.
As a developing method using a dry toner for image forming apparatuses using an electro-photographic process, there has been proposed a development method in which, when, by using a magnetic roller (toner supply roller), developer is transferred onto a developing roller disposed out of contact with a photosensitive drum (image carrier), a thin toner layer is formed by transferring only non-magnetic toner particles onto the developing roller, leaving magnetic carrier particles on the magnetic roller, and, in an opposing region (developing region) where the developing roller and the photosensitive drum face each other, toner particles are caused to jump to, and adhere to, an electrostatic latent image on the photosensitive drum by an AC electric field.
In recent years, more and more complicated configurations have come to be adopted in image forming apparatuses along with the progress in color printing and high-speed processing. In addition, for higher-speed processing, it is indispensable to achieve higher-speed rotation of a toner stirring member within the developing device. In particular, according to a developing method described above in which a two-component developer containing magnetic carrier and toner is used, and in which a magnetic roller which carries the developer and a developing roller which carries only the toner are used, in an opposing portion of the developing roller and the magnetic roller, a magnetic brush is formed on the magnetic roller, and by the magnetic brush, only the toner is caused to be carried on the developing roller, and further, the toner left unused for development is peeled off from the developing roller. Thus, with this method, toner particles are apt to float in the vicinity of the opposing portion of the developing roller and the magnetic roller, and such floating toner particles accumulate around a trimming blade (a regulation blade). If the accumulated toner particles adhere to the developing roller in a condensed manner, they may eventually fall and cause an image defect.
There is known a developing device using a two-component developer containing magnetic carrier and toner, and using a magnetic roller carrying the developer and a developing roller carrying only the toner, the developing device including, as a solution to the above-described problem, a toner receiver support member facing the developing or magnetic roller, a toner receiver member disposed along a longitudinal direction of the toner receiver support member to receive toner fallen from the developing roller, and vibration generating means for vibrating the toner receiver member.
There is also known a developing device having a film member fitted to an inner wall portion (sleeve cover) of a developing container, the inner wall portion opposed to a developing roller, such that, when a drive gear train for driving the developing device is rotated, a link member is caused by a link member drive mechanism to intermittently pull the film member to cause the film member to longitudinally reciprocate to thereby shake off toner particles accumulated on the film member.